One of the recent advances in cardiopulmonary bypass surgery has been the introduction of a technique called cardioplegia administration. A very cold solution typically in the range of 4.degree. C. is delivered under controlled conditions to the coronary arteries via the aortic root. The solution stops the heart through chemical action and also cools the heart to 10.degree.-14.degree. C. to minimize deterioration of the heart muscle during the operation. As the surgery progresses, it may become necessary to administer an additional amount of cardioplegia solution to again cool the heart and in some instances there is a continuous administration of the cardioplegia solution.
In order to determine if the heart has been adequately protected by cooling, it is beneficial to monitor the temperature at various sites on the heart itself. Since the surface temperature may not be a true indicator of the protection of the heart, it is important to monitor the inner temperature of the heart muscle itself rather than the surface temperature.
Existing devices are electronic in nature. Typical devices utilize a probe consisting of a thermocouple hypodermic needle with a cable running out of the surgical field to an amplified and display system. Typically the probe is quite fragile and must be resterilized prior to each use, with a limited number of uses.
The present invention contemplates a temperature indicator which is self-contained and mountable directly on the heart organ in a position to be readily monitored by the attending surgeon. The device eliminates the need for any electrical connections and the attendant risk involved with such connections. The indicator is relatively inexpensive and thus can be furnished in sterile condition and disposable so that sterilization is not needed. It can also be utilized with a luer fitting to monitor temperatures in the cardioplegia perfusion circuit.
Other objects and features of the invention will be evident in the following description and claims in which the invention is described together with details to enable persons skilled in the art to practice the inventon, all in connection with the best mode presently contemplated for the invention.